Spoilers follow for Doctor Who – you have been warned!
As expected, the episode saw Tennant’s incarnation of the Doctor regenerate at the end, paving the way for Ncuti Gatwa to take the reins as the 15th version of the Time Lord.
However, in an unprecedented move for Doctor Who, Tennant’s Doctor does not disappear, but instead splits in half, with Gatwa’s Doctor emerging from his body and existing independently.
Fans have speculated that the move will allow Tennant to continue appearing as the Doctor in spin-off projects, while Gatwa helms the main Doctor Who brand. However, with the twist contravening established lore, it’s been a divisive decision among fans of the show.
Tennant, alongside series showrunner Russell T Davies and producer Phil Collinson, recorded a full-length commentary for the episode, which is available to stream on BBC iPlayer.
“It was a very closed set,” showrunner Russell T Davies recalled, as the regeneration scene begins to show on screen. “There will be an awful lot of people who don’t know what’s going to happen. The vast majority. And it plays with them so much here.
“We were going to see if we could get this on the news afterwards.”
Davies claimed that the “fussing” over the special effect where Tennant’s character gets pulled in two was “really difficult”.
Collinson explained that there had been different versions of the scene trialled, including ones where he was “ripped apart”, which were deemed “too violent”.
Speaking about Gatwa’s introduction, Tennant recalled: “He just walked on and started.
“It was so nice, the sort of joy of this,” the Scottish actor added.
In a four-star review of the episode, Ed Power wrote: “The big question is what it all means for Gatwa’s stint as the Doctor. Tennant’s 14th Doctor has gone off to recuperate with Donna and her family, having apparently come down with interstellar PTSD. Yet he’s very much around and could come charging back at any moment – intriguing and very, very Marvel (no coincidence perhaps that the shift in lore comes as Disney + acquires global distribution rites for the franchise).
“Yet it also implies that the BBC doesn’t quite trust Gatwa enough to hand him sole custodianship of the sci-fi flagship. Not that the Sex Education star seems too bothered, though. Even without trousers, he’s devilishly good fun – the Doctor we know and love but with enough charm to put his stamp on the character. He’s great – in the meantime, let’s give Davies and Tennant the benefit of the doubt and see how this Double Doctor strategy plays out.”
Doctor Who is available to stream on BBC iPlayer, along with the video commentary.